Art of heat-stabilization of polyvinyl halide resins



fully bind evolved hydrogen chloride. This agent cannot United StatesPatent 01w are:

obtained from the diiferent trade sources, have been found 2,989,497satisfactory. ART OF [EAT-STABILIZATION F POLYVINYL Such epoxides, asstrong hydrochloric acid acceptors,

HALIDE RESINS have in common the oxirane function which can be repre-Richard Milton Lycette, Villa Park, Ill., assignor to Continental CanCompany, Inc., New York, N.Y., a cor- 5 Sented as follows poration ofNew York No Drawing. Filed Nov. 25, 1957, Ser. No. 698,327 fi 3 Claims.(Cl. 260-453) The structure for a typical low molecular weight bis- Thisinvention relates to resin compositions containing phenolA/epiehlorohydrin type resin can be given as:

vinyl halide in polymer form, and is characterized by im- The structurefor a typical phenol-formaldehyde/epiprovement of stability against thechemical breakdown chlorohydrin type polymer resin can be given as: ofthese resins. This stability is manifested by greatly increasedresistance to charring or color degradation upon 0 heating.

It is know that serious primary degradation of a polymer O OHI'Gcontaining vinyl chloride, upon heating, occurs by a partial chemicaldecomposition and the splitting oif of hydrogen chloride from themolecule. The degradation of polyvinyl chloride and related copolymersis a complicated n reaction, since in the first stage it is a freeradical mech- 0 0 anism and in the later stages an ionic mechanism.Autocatalysis of degradation has been stated to occur by the action ofliberated hydrogen chloride, but it is a present belief that hydrogenchloride only enhances degradation when there are present in the systemmetals which can be converted to metal chlorides. According to thisinvention, a component is added to the system which can help- Anyfat'soluble optho'subsfituted azo dye may be used which has aromaticnuclei joined by one or more azo structures (N=N) and with one of thefollowing possible radicals substituted ortho to the azo group: OHNO NHCOOH. Such radicals may be attached to one or two carbons ortho to theazo group. Examples of such dyes are 1-naphthylene-azo-Z-naphthol(commercially available as Resinoil Brown Y Dye), l-phenyl-azo-Z-naphthylamine (commercially available as FD & C No. 3),1-o-nitro-p-tolylazo-2-naphthol (commercially available as D & C RedNo.35).

A typical azo dye is the so-called Resinoil Brown Y Dye made by couplingB-naphthol with a-naphthyl diazonium salts.

be 100% effective; and thus, some hydrogen chloride Will be available tocombine with any metals present to form the corresponding metal halidesand promote degradation.

According to this invention, another agent is also used in conjunctionwith the acid acceptor, which can couple with or inactivate these samemetals and thereby significantly increase the heat stabilization of suchfilms. 40

Stabilizers are known which are capable of delaying or retarding thisprimary degradation, many of which are alkaline or basic in nature andserve to neutralize such released acid. Common also to the literatureare certain compounds called chelating agents which are able to combinewith metal ions to form ring structures in which the metals are verystrongly bound.

It has been found that the azo compounds or the N:N epoxides, when usedseparately, each have a protective effect but do not produce acommercially satisfactory stabilization at desirable higher levels ofheat treatment. The combination of such compounds has been found to makeit possible to stop vinyl degradation at such elevated Such azo dyes actas ehelatihg agents, Whieh action may temperatures- Accordmg to Presentmventlon the be ascribed to a molecular structure by which availablecoordinate use of the stabilizers, each in an amount which iron, orother metal in the reaction System, is bound as a total does not degradethe vinyl resin composition strongly between the ortho substituents andthe azo strucf 105s of the Yinyl resin PP leads to a Syner' ture. Theeffect is believed to be that of firmly tying up P. cumulatlve iwlth.gTeafly Improved heat the metal (such as iron copper tin, etc.) sothat the free stability so that commerclally satisfactory results areatradical mechanism doesnot operate tamed Homopolymer polyvinyl chloridecan form the sole or Any chemical compound which 18 a strong hydrochloncprmc1pal component of the vinyl resin base; or this vinyl acid acceptor,soluble in vinyl resin systems, and stable under the elevated heattreatments is satisfactory. Exresin base can be copolymer or vinylchloride with amples of Sueh compounds are epoxides which have thesmaller amounts of such mono-functional unsaturated bisphenolA/epichlol-ohydrih or the h 1 f 1d compounds as vinyl acetate,vinylidene chloride, ethyl hyde/epichlorohydrin type configurations.Best results Y f0rmate,and thelike- These P are obtained in the range ofto 210 epoxide equivtions, with the corresponding other vinyl halidepolymers, alent weight. Stable epoxide resins of the types, as arereferred to herein as polyvinyl halides or vinyl halide 3 resins, as thedominant ingredient is vinyl halide in a polymer form.

Polyvinyl chloride resin is mixed with 2 percent of the epoxide resinand 0.375 percent of the azo compound, the

by the fact that cures were possible above the 305 dcgrees F. level withno burning occurring at 360 degrees F. with some formulations andappropriate time/temperature values. Successful stabilization has beenachieved even proportions being based on the weight of the solids or 5at a temperature of 445 degrees F. with 5.0 percent non-volatile matterof the vinyl resin. Any commercially Resinoil Brown Y Dye and 20.0percent Epon 828. available epoxide resin of the bisphenolA-epichlorohydrin The employment of the epoxide resin with the polyvinyltype having an epoxide equivalent of about 200' is 'satishalide resins,although offering some stability, is not suffactory: a side effect ofthe epoxide resin is to increase ficient for can manufacturing purposes.The azo dye and the adhesion of the vinyl resin composition film tometal vinyl resin compositions also exhibit some improvement surfacespossibly due to the action of polar groups in the of stability againstheat degradation but not enough for molecule. can making purposes. Itwill be understood that increas- Expefiellce has Shown that the 1156 Ofullstabililed Vinyl ing the quantity of the additive relative to thepolyvinyl resins on plain tin surfaces is not practical d e to heahalide resin does not increase the stabilizing effect in the degradationat normal baking temperatures of 305 degrees ame relativ ro ortion, sothat such increases do not 14 minutes, Or 360 degrees F for 11/2minutes, P lead to satisfactory results; and in addition, larger amountsbaking time being noted. The following tabulations show of the additivemeans decrease in the amount of polythe improvement effected by theadditives: vinyl halide resin present, with diminution of the desiredeilect of the polyvinyl resin which is the material relied upon forproducing the protective coating. The azo dye Cmmsitlon P- (Paris by andepoxy resins, however, exert a synergistic action in weight on solidsbasis) Formulations compounds with polyvinyl halides to increase theover-all 1 2 3 4 effectiveness of the combination, which requires onlysmall amounts of the components, e.g. 0.5 to 5.00 percent 5 of theepoxide and 0.187 to 5.000 percent of the azo dye, 10 on the basis ofthe weight of the vinyl halide resin. When the basic resin compositionfilm preferably has the com- ResinoilBrownYDye 0.315 bined effects ofvinyl halide and epoxy resins, e.g. for

adhesion, the epoxide content can be as high as 50 percent of the weightof the vinyl halide resin. lqllgccgiiglolyvinyl chloride and polyvinylacetate copoiymer with This unique action of the azo dyes in thecomposite is H188 C VYHH-Polyvinyl chloride and polyvinyl acetatecopolymer. further exemphfied by other comparative tests, as shownVAGH-Hydrolyzed polyvinyl chloride and polyvinyl acetate 00- by thefollowing tabulations. polymer.

The basic formulas employed for these examples were The results of thecuring test in a circulating air oven as follows: at 360 degrees F. for14 minutes peak bake were as follows:

Composition No. (Parts by FORMULA AS USED ON #25 ELECTROTIN PLATE weighthas) Composition Film Behavior 5 6 7 8 VMCH Resin 5 5 5 5 Excesswe i e-VAGH Resin.-- 10 1o 10 10 gg g gggYHERRes 85 s5 s5 s5 oxy esin e 2 2 2 2N0 s- B Y Dye- 375 FORMULA AS USED ON GM BLACK IRON PLATE stabilizers(Misce Composition Film Behavior Excessive Burning. Dye Used In ModerateBurning. Formula Common Name Chemical Name or Structure Slight Burning.Composition No Burning.

5 Sudan Brown (Resinoil 1-Naphthy1ene-azo-2-naph- Brown Y Dye). tho

6-1 Methyl Red p-Dlmethyl-amlno-azo-ben- The film behavior in all thesestudies is based on an average film thickness of 3.5 mils.

When used on #25 Electrotin plate there was no burning when compositionNo. 4 was employed, namely, dye and epoxy resin together with the vinylhalide resins. When either was used separately, moderate burning of thefilm took place. With neither stabilizer, excessive burning was observed(composition No. 1). On this plate surface the advantage of the dye overthe epoxy resin, used individually, was not significant. Also when thesesame compositions were cured on CMQ black iron plate, the results wereessentially the same, with no burning occurring in No. 4, where both dyeand epoxy resin were used. When neither were used, excessive burning wasseen. Apparently the dye may be acting to complex free metal ions bychelate formation, and preventing catalytic degradation of the polyvinylchloride resin. Stability can be satisfactorily achieved on steelsurfaces by the joint action, as it is on tin plate surfaces.

The stabilizing effects of such a system is emphasizedzene-o-oarboxylic-acld. i Phenyl azo 2 naphthylamine.

1 o Tolylazo 2 naphthylamine.

Tetrazo-benzene-B-nnphthol.

FD & 0 Yellow #3 FD & 0 Yellow #4 Sudan Red D & 0 Red #18.......... Xlylazoxylylazo-2-naphthol.

D & 0 Red #35 l-iiliiliitro-p-tolylazo) 2-naph- Rhodamine B-Red. 3Ethostearate ofO-o-carboxyphenyl-G-diethylamlno-Ziethylimlno-3-isoxanthene.

7-2 Methyl Cresol Purple... m-Cresolsulionphthaleiu.

7-3 Quinalizarm Red 1,2,5,8-Tetrahydroxyan-thraquinone.

7-4 D & C Green #6.. 1,4 Bis (p-toluino) anthraquinone.

7-5 D 8: C Red #19 3 Etho-ohlorlde oflip-carboxyphenyl-(i-dlethylamlno-S-ethyllmlno-ii-lsoxnnthene.

7-6 D & 0 Red #37 3Ethostearate oi9-o-carboxyphonyl-fi-diethyl-amlno-B-ethylimino-B-lsoxanthene.

7-7 Satranlne O(Red). Oxidized p-Tolyiene-dlurnlne,

Aniline, undo-Toluidinc.

Stability of these compounds not certain in heated films.

These materials were cured in an air oven at 360 degrees F. for 14minutes (peak bake time). When used on #25 Electrotin plate, the resultswere:

Formula Compositions Heavy Film Burning Excessive Burning.

1 (Control) 5 N Burning.

. Excessive Burning.

The efiect of the co-presence of the epoxy resin and azo dye can also becompared with the effects of various lead and non-lead stabilizers, andof other recognized chelating agents. In the following examples, a resinmixture containing polyvinyl halide proportioned as in Formulas to 8above, was prepared with 2 parts by weight of the same epoxy resin(Shell Epon 828), and 0.375 percent (solids basis), of the atollowinglead type stabilizers added. The coatings were then baked for 14 minutes(peak bake time) at 360 degrees F. in an air oven, with the results:

The barium cadmium organic complexes used above were Clarite, Provinite,and Flomax 25, all products of the National Lead Company.

The synergistic eitect of the azo dyes is likewise established bycomparison with the effects of other metal chelating agents. Using thevinyl resin composition of Formulas 5-9 above, with 2 parts by weight ofepoxy resin (Shell Epon 828) and 0.375 percent (solid basis), of thefollowing additives, and baking for 14 minutes (peak bake time), at 360degrees F. in an air oven, the results on a comparative scale were: 7

Burn Rating Burning Noted 5 (Resinoil Brown Y Dye Control) 10-12-Quin0linol 10-2 2-Nitroseo-1-naphthoL- 10-3 3-Salioylaldoxime.... 18:?1,10 Phenanthroline.

10-6 107 O-NitrOphenOL-.- 10-8 10-10 1-Phenyl-1,3-butanedi 10-11Salicylidene acetamide. 10-12 B-Quinolinol 10-13 2,4-Pentanedione..

Stability of this compound not certain in heated film.

.The above numerical values for burn rating were fixed by setting 10 asa condition of no burning, and 0 as a condition where the film waspercent burned over its area.

These tests show that no burning occurred on heavy films where an azodye similar in structure to the Resinoil Brown Y Dye, or Sudan Brown,was incorporated into the film along with the epoxy resin. Where dyesnot having the stated azo type structure were employed, serious burningoccurred. Also where other types of compounds such as diphenylamine,lead carbonate, urea, catechol, Sustane, and hydroquinone werecomparatively employed, there was excessive burning of extensive filmareas.

The use of azobenzene in place of the ortho substituted azo dyes did notgive stabilization, further indicating the necessity of activeortho-s-ubstituted groups on the aromatic nuclei to effect stability.

A further test on the use of epoxides, which are powerful acidacceptors, shows the importance of structure and epoxide number in heatstabilization. All the compositions represented below employed a resinmixture containing polyvinyl halide proportioned as in Formulas 5 to '8above. To this vinyl halide resin was added 2 percent by weight of eachof the following epoxide resins and 0.375% by weight of the ResinoilBrown Y Dye. The coatings were then baked on tin plate for 14 minutes at360 F. in a circulating air oven with the following results:

1 Synthesized in the laboratories of Continental Can 00., Inc.commercially available.

Not

The superiority of either the bisphenol A/epichlorohydrin resins (5, 7,8, 9, 10) or the phenol-formaldehyde/epichlorohydrin resins (6) over theother types of epoxides tested is evident. The relative advantage of thebisphenol A/epichlorohydrin type resins having the lowest epoxideequivalents is also exhibited. These results show that such epoxideresins having an epoxide equivalent of about 170 to 210 are required forthe maximum effect. The combined additives can be stated as including aheatstable epoxy resin with an epoxide equivalent weight in the range of170 to 210, and an azo compound in which the azo group is joined toaromatic nuclei, these nuclei having functional ortho substituents.

The above examples of successful practice are given by way ofillustration; and it will be understood that the invention is notlimited thereto, within the scope of the appended claims.

What is claimed is:

1. A vinyl chloride resin composition stabilized for resistance againstheat degradation during baking at 305 degrees F. for 14 minutes,including a heat-stable epoxide resin selected from the group consistingof bisphenol A/epichlorohydrin and phenol-formaldehyde/epichlorohydrinhaving an epoxide equivalent weight of 170 to about 210 in an amount of0.5 to 20.0 percent by Weight of the vinyl resin, and a metal chelatingazo dye in an amount of 0.187 to 5.0 percent by weight of the vinylresin, said azo dye having a structure comprising two aromatic nucleargroups each having a benzene ring and having 6 to 10 carbon atoms in thenuclear group, said groups being connected by an azo group and one grouphaving a functional organic radical selected from the class consistingof OH, N0 NH and COOH located in the ortho position relative to the azoconnection.

2. The method of stabilizing a vinyl chloride resin composition forresistance against heat degradation during baking at 305 degrees F. for14 minutes which comprises mixing therewith a heat-stable epoxide resinselected from the group consisting of bisphenol A/epichlorohydrin andphenolformaldehyde/epichlorohydrin having an epoxide equivalent weightof to about 210 in an amount of 0.5 to 20.0 percent by weight of thevinyl resin, and also mixing therewith a metal chelating azo dye in anamount of 0.187 to 5.0 percent by weight of the vinyl resin, said azodye having a structure comprising two aromatic nuclear groups eachhaving a benzene ring and having 6 to 10 carbon atoms in the nucleargroup, said groups being connected by an azo group and one group havinga functional organic radical selected from the class consisting of OH,N0 NH and COOH located in the ortho position relative to the azoconnection.

3. A vinyl chloride resin composition stabilized for resistance againstheat degradation during baking at 305 degrees F. for 14 minutes,including a heat-stable epoxide resin selected from the group consistingof bisphenol A/epichlorohydrin and phenol-formaldehyde/epichlorohydrinhaving an epoxide equivalent weight of 170 to about 210 in an amount of0.5 to 5.0 percent by weight of the vinyl resin, and a metal chelatingazo dye in an amount of 0.187 to 5.0 percent by weight of the vinylresin, said azo dye having a structure comprising two aromatic groupseach having a benzene ring and having 6 to 10 carbon atoms in thenuclear group, said groups being connected by an azo group and one grouphaving a functional organic radical selected from the class consistingof OH, N0 NH and COOH located in the ortho position relative to the azoconnection.

References Cited in the file of this patent UNITED STATES PATENTS2,530,353 Havens Nov. 14, 1950 2,590,059 Winkler Mar. 18, 1952 2,595,619Voorthuis May 6, 1952 2,719,090 Morehead Sept. 27, 1955 FOREIGN PATENTS1,042,357 France Oct. 30, 1953

1. A VINYL CHLORIDE RESIN COMPOSITION STABILIZED FOR RESISTANCE AGAINSTHEAT DEGRADATION DURING BAKING AT 305 DEGREES F. FOR 14 MINUTES,INCLUDING A HEAT-STABLE EPOXIDE RESIN SELECTED FROM THE GROUP CONSISTINGOF BISPHENOL A/EPICHLOROHYDRIN AND PHENOL-FORMALDEHYDE/EPICHLOROHYDRINHAVING AN EPOXIDE EQUIVALENT WEIGHT OF 170 TO ABOUT 210 IN AN AMOUNT OF0.5 TO 20.0 PERCENT BY WEIGHT OF THE VINYL RESIN, AND A METAL CHELATINGAZO DYE IN AN AMOUNT OF 0.187 TO 5.0 PERCENT BY WEIGHT OF THE VINYLRESIN, SAID AZO DYE HAVING A STRUCTURE COMPRISING TWO AROMATIC NUCLEARGROUPS EACH HAVING A BENZENE RING AND HAVING 6 TO 10 CARBON ATOMS IN THENUCLEAR GROUP, SAID GROUPS BEING CONNECTED BY AN AZO GROUP AND ONE GROUPHAVING A FUNCTIONAL ORGANIC RADICAL SELECTED FROM THE CLASS CONSISTINGOF OH, NO2, NH2 AND COOH LOCATED IN THE ORTHO POSITION RELATIVE TO THEAZO CONNECTION.